Single action pneumatic riveter



May 5, 1941 O. E. CLARK 2,241,184

SINGLE ACTION PNEUMATIC RIVETER ATTORNEY May 6, 1941.

O. E. CLARK SINGLE ACTION PNEUMATIC RIVETER 4 Sheets-Sheet 2 Filed Oct.- 19, 1939 ATTORNEY May 6, 1941. o. E. CLARK SINGLE ACTION PNBUMATIG RIVETER Filed Oct. 19, 1939 4 Sheets-Sheet 3 K. R 1 N Q a %%\t mE. MM -0M mm NN MM. NM v ,uw J Il* h%.\ mw l @K mm uw .QQ .w

' May 6, 1941. o. E. CLARK 2,241,184

SINGLE ACTION PNEUMATIC RIVETER Filed Oct. 19, 1939 4 Sheets-'Sheet 4 T151 .4. f7 M z5 a Z7 \\\NW lNvENToR ATTORNEY OMAR E, (2A/2K.

Patented May 6, 1941 2,241.1 smGLE Ac'rIoN rNEUMA'rrc aivE'rEn Omar E. Clark, Detroit, Mich., assigner to Chicago Pneumatic Tool Company, New York, N. Y., a corporation of New Jersey Application October 19, 1939, Serial No. 300,185

`22 Claims.

This invention relates generally to fluid pressure operated hammers of the single action type for performing riveting and similar operations and relates more particularly to control means for simplifying and-improving the action of suoli hammers.

Single action or one-shot riveters are used principally in air-craft construction where the majority of the rivets used are small enough to be headed with one or two blows. The usual one-shot tool comprises an elongated cylinder, within which a hammer piston reciprocates, and a handle, connected to the cylinder and containing throttle valve mechanism for controlling the flow of pressure fluid to the ends of the cylinder. The air pressure in back of the hammer piston varies during the impact stroke whereby the force of the blow delivered to the rivet set or working implement is usually less than that theoretically attainable if the air were at the maximum pressure throughout the entire stroke. One of the causes of the pressure variation in tools of ordinary construction is the fact that the hammer piston is permitted to drift forward as soon as the throttle valve starts to open so that by the time that maximum pressure is built up in the rear end of the cylinder th-e piston has already completed a portion of its stroke. The force of the blow depends largely, therefore, upon the dexterity of the operator in manipulating the throttle lever. The effects of this drifting may be reduced by the provision of yieldable mechanism for retarding initial movement of the pis- .ton which, however, does not obviate the necessity for skillful manipulation by the operator or eliminate variations in the force of the blow.

Among the objects of the invention are to increase the power and reduce the air consumption of a one-shot tool of a given size.

Another object is to enable the tool to deliver an impact without the loss of power occasioned by premature initial movement or drifting of the hammer piston.

A feature of the invention is e positive lock i preventing the hammer piston from starting on its impact stroke until a predetermined degree of pressure has been established behind the piston.

A further object is to perm-it the force of blow by the piston to be so delicately adjusted that a substantially perfect rivet head may be driven without leaving the imprint from the rivet set on the soft aluminum sheets being riveted together. y

A still further object of the invention is to enable the degree of pressure at which the hammer piston isreleased to be altered at will in order that the momentum of the piston may be correspondingly altered to suit the requirements of a particular size and kind of rivet.

The present tool is especially suited for use in connection with aluminum alloy rivets. Rivets of such composition have the property of changing their hardness. When rst heat treated, the metal is extremely soft but begins to harden almost immediately and will reach maximum hardness in a few hours. As the alloy rivets in a particular lot gradually harden, the operator may make corresponding adjustments from time to time in the force of blow by the piston.

Still another object of the invention is to obviate the necessity for a high degree of skill on the part of the operator. In accordance with this invention, the mechanism which controls the force of blow operates in the same manner irrespective of whether the operator moves the throttle lever quickly or slowly, and is not affected ordinarily by fluctuations in air pressure in the factory main or supply line.

Another feature resides in a calibrated adjusting wrench for the pressure regulating mechanism.

Still another feature resides in a pressure chamber or reservoir forming an energy accumulator and cooperating in the delivery of energy to the hammer piston, at a rate exceeding the rate of supply of potential energy by the air hose, during the power stroke of the piston.

Another object of the invention is to prevent the return of the throttle control mechanism to normal or closed position until the cycle of operation is completed. In carrying out this object there is provided, in the illustrative embodi- ,f ment of the invention, a yielding means urging the throttle valve to closed position, a, latch adapted to retain the throttle valve in position to admit air to the cylinder in a direction to return the hammer piston, and means, operable by the piston at the end of its return stroke, for disabling the latch.

Other objects and features of the invention will be more apparent from the following description when read in conjunction with the accompanying drawings and appended claims.

In the accompanying drawings which illustrate a preferred embodiment of the invention:

Fig. 1 is a view, in longitudinal section, of the tool, showing all parts in normal position;

Fig. 2 is a view similar to Fig. 1. showing the throttle control lever in fully actuated position.

and the parts in the position they assume during the impact stroke after the release of the hammer piston;

Fig. 3 is a view similar to Figs. 1 and 2, showing the parts in .the position they assume just prior to the end of the return movement of the hammer piston;

Fig. 4 is a view similar to Figs. 1, 2 and 3, showing all parts in the position they assume at the end of the return movement of the hammer piston just prior to the rebound of the hammer piston from overthrow position to normal position;

Fig. 5 is an lenlarged sectional view corresponding to Fig. 3, showing the pressure iluid conducting passageways diagrammatically;

Fig. 6 is a longitudinal section, showing principally the hammer piston latching means, and is taken substantially along the broken line 6-6 of Fig. 2, looking downward;

Fig. 7 is a cross-sectional view, looking forward, of the supporting element for the hammer piston latch;

Fig. 8 is a longitudinal section of the supporting element and is taken along the line 8 3 of Fig. 7 i

Fig. 9 is a view, in elevation, of the wrench used to adjust a control device of the tool in order that the force of the blow delivered may be regulated;

Fig. 10 is an end view of the wrench shown in Fig. 9; and

Fig. 11 is a fragmentary view, in section, of the adjusting wrench, and is taken substantially along the line I |II of Fig. 9.

The present invention is disclosed as embodied in a small riveting hammer of the one-shot type. As shown in Fig. 1 the hammer comprises generally an elongated cylinder I5 formed with a longitudinal opening or chamber I6 within which a hammer piston I1 reciprocates. Supported at the front end of the cylinder |5 and in axial alignment therewith is a rivet set |'8 one end of which extends into the piston chamber |6 in position to be struck by the piston I1. The rivet set I8 is movable within a bushing I9, positioned in the front end of the cylinder i5, and is formed with a collar 2| which engages the outer end of the bushing to limit rearward movement of the rivet set. Forward movement of the rivet set is limited by engagement of the collar 2| with the outer coil of the usual retainer 22 which encircles the front end of the cylinder I5. The rear end of the cylinder I5 extends into a counterbore 23 formed in the front end of a handle 24. The handle 24 and the cylinder 5 are secured together by means of a sleeve 25 which encloses the adjacent ends of the two elements. The sleeve 25 is threaded on to the handle 24 and limits relative movement of the cylinder I5 through a retaining ring 26 which engages complementary recesses in the sleeve and cylinder.

The handle 24 is of generally right angle construction, having a downwardly extending grip portion, containing pressure iluid conducting passages, the throttle control mechanism and other control elements later to be described. A main bore in the handle 24 above the grip portion thereof, forms a pressure chamber 21 which opens directly into the piston chamber I6, within cylinder I5. To eifect reciprocation of the hammer piston I1 pressure uid, preferably compressed air, is directed through the grip portion of the handle and is admitted alternately to the pressure chamber 21 and to the forward end of the piston chamber I6 at a' point in front of the hammer piston I1. The pressure fluid is introduced into the tool through a flexible hose H connected at one end to a suitable source of compressed air and connected at its other end to a plug 28 screwed into the lower end of a bore 29 formed in the grip portion of the handle. The air flows .through a port 30, in the plug 28, into the bore 29 and, under the control of a throttle valve 3|, is admitted to one or another of a pair of passages 32 and 33 (see Fig; 5) or is prevented from entering either of these passages. The passages 32 and 33 extend upwardly through the handle 24, the passage 32 opening into the pressure chamber 21 while the passage 33 communicates with a longitudinal passage 34 formed in the wall of the cylinder I5. The forward end of the passage 34 communicates, through a valvel assembly 35, with the forward end of the piston chamber |6. By reason oi' this arrangement of passages air, when directed through the passage 32, acts to drive the hammer piston I1 forward through its impact stroke and, when directed through the passage 33, acts to move the hammer piston rearward through. its return stroke.

l,The throttle valve 3|', which controls the ow o'f air -to the passages 32 and 33 is of the piston type and is movable vertically within a bushing 36 positioned in the bore 29. Extending throughout the length of the valve 3| is a longitudinal opening 31 the lower end of which is closed by a plug 38. Communication between the longitudinal opening 31 and the bore 29 is established through a set of ports 39 formed in the valve 3| near its low er end. A collar 4I is formed on the lower end of the valve 3|, -below the ports 39, and is adapted to engage the lower end of the bushing 36 to limit upward movement of the valve and to prevent the flow of air through the ports 39. A compression spring 42 interposed between the lower end of the valve 3| and an inner shoulder of the plug 28 urges the valve upward to the normal position of Fig. l, in which position communication between the bore 29 and valve opening 31 is cut olf by reason of the engagement of collar 4I with the lower end of bushing 36. Also formed in the valve 3| are two more sets of ports 43 and 44 which, in cooperation with associated bushing grooves, establish communication between the valve opening 31 and the respective passages 32 and 33. Referring particularly to Fig. 5, it will be seen that the lower ends of the passages 32 and 33 open into respective grooves 45 and 46 formed in the inner surface of the bore 29. In alignment with the grooves 45 and 46 are respective sets oi' ports 41 and 48, in the bushing 36, which through associated grooves formed in the inner surface of the bushing .communicate with the interior of the bushing. By movement of the valve 3| within the bushing 36 one or another of the sets of ports 43 and 44 may be brought into alignment with its respective set of bushing ports to direct air to one or anotheroi' the passages 32 and 33. The ports are so arranged that the setting of the valve 3| in position to admit air to one passage serves also to prevent the flow of air to the other passage. The valve 3| is formed, in addition to the ports 33, 43, and 44, with a groove 49 cut in the outer surface of the valve at a point between the ports 39 and 43. This groove communicates, through a set of bushing ports 5| and groove 62, with a passage 53 leading to exhaust. As shown in Fig. 1, in the upper or normal position of the valve 3| the groove 49 uncovers both sets of bushing ports 41 and 5I and so connects the passage 32, and thereby the pressure chamber 21. to exhaust.

The valve 3| is operated by a manually operablecontrol lever, or trigger, 54 locatedin a slotted portion 55 of the grip portion of the handle 24. The trigger 54 is movable about a pivot 55 and is formed withy a rearwardly extending finger 51 which overlies the upper end ofl the valve 3| and the upper reduced portion of a plunger 55 which closes the upper end of the valve opening 31 (Fig. 5). A spring 53 positioned within the opening 31 between the plug 38 and the lower end of the plunger 58 urges the plunger toward the finger 51. An abutment collar 5| supported at the upper end-of the valve 3| limits upward movement of the plungery 58. f

Due to the pressure of the springs 42 and 53 the several elements comprising the throttle control mechanism normally stand in the position shownl in Fig. 1. To initiate a cycle of operation the trigger 54 is depressed from the Fig. 1 to the Fig. 2 position. In moving to the fully actuated position of Fig. 2 the finger 51 of the trigger first moves the plunger 58 .downward through the opening 31 and then acts upon the upper surface of the abutment collar 5| todepress the assembly comprising'valve 3| and plunger 53, as a unit. The initial relative movement of the plunger 58 serves to close the ports 44 while the sub-l sequent movement of the valve 3| serves to bring the ports 43 opposite the bushing ports 41, and to place the-ports 35 below the bushing 35 to admit air to the valve opening 31. The air flows from the opening 31, out the porte 43 to the passage 32 and is thereby directed to the pressure chamber 21 where it is stored momentarily and from whence it later expands to drive the hammer piston I1 through its impact stroke. After the impact has been delivered the trigger 54 is released by the operator and the valve assembly is free to rise under the action of the springs 42 and 59. As shown in Fig. 3. the plunger 53 rises to its normal position relative to the valve immediately upon the release of the trigger whereas the valve 3| is automatically held in a. partly actuated position in order that air may be directed through the passage 33 to `effect the return of the hammer piston.

The means for holding the valve 3| in partly actuated position includes a latch 52' pivoted, on a pin 63, to swing in a plane parallel to a side wall of the slotted portion 55. 'I'he latch 52 is urged in a counter-clockwise direction by a spring 54 and is formed with a shoulder 55 adapted to engage the upper end ofthe valve 3 I'. As shown in Fig. 1, the shoulder 55 of the latch 52 normally abuts against the side of the valve 3|, near its upper end, and is held out of locking position. Upon depression of the valve, however, the latch is permitted to rock in a counter-clockwise direction to the position shown in Figs. 2 and 3 where the shoulder 55 overlies the upper end of the valve. When the trigger 54 is released, the valve V3| moves toward normal position but is prevented from completing its return movement by the latch 52 which holds the valve in the position shown in Fig. 3. In this position of the valve, the ports 43 are out of alignment with their associated bushing ports 41, and so closed, whilevtheports 44 have been brought opposite the bushing ports 48. Also, the ports 35 still extend slightly below the lower end of the bushing 35 and air continues to now into the opening 31. Since. the ports 43 are now closed and the plunger 55 no longer covers the ports 44, the air from the opening 31 in the position shown in Fig. 3 the pressure cham- 21 is connected to exhaust through the sets of ports 41 ber groove 49 which uncovers both and 5| at this time.

The air will continue to flow in a direction to return the hammer piston as long asl the valve 3| is held by the latch 52. Disabling of the latch 52 is brought about automatically by the hammer piston as it reaches the end of its return stroke. The rear end of the hammer piston is formed with a head 55 adapted to extend into the pressure chamber 21 and engage the upper front end of a lever 51 pivotally mounted between a pair of arms 33 of a supporting bracket 53 (see Figs. 6, 7 and 8). The lever 51 extends rearwardly beyond its pivot point and overlies the upper end of a spring pressed lplunger 1| which passes downwardly through a bushing r'42 and in turn overlies a forwardly extending arm of the latch 52. As the hammer piston reaches the very end of its return stroke (shown in Fig. 4) the head 55 thereof strikes the' lever 51 and rocks it in a counter-clockwise direction to depress the plunger 1"| and thereby disable the latch 52. Upon disabling of the latch. the valve 3| immediately rises to the normal position of Fig. 1, thereby cutting o the supply of air to the opening 31 and holding the latch 52 in disabled position.

The valve assembly 35 which controls the now of air to and from the forward end of the piston chamber l5 is similar in construction and operation to that disclosed in the patent to E. W. Stevens No. 2,101,159, issued December '1, 1937, and therefore will be described only briefly herein. The cylinder I5 is formed, near its front end, with a boss 13 containing a recess 14 which opens, through a port 15, into the forward end of the piston chamber I5. 'I'he outer end of the boss 13 is closed by a cap 15 and the area thus4 enclosed by the cap communicates with the passage 34 through a passage 11. Mounted within the recess 14 is a hollow valve 13 movable to an open and closed position with respect to the port 15 and an exhaust port 13. When air is directed through the passages -33 and 34 to return the hammer piston l1 it ows through the passage 11, around the notched lower edge of valve 13. to the recess 14 and presses the valve upward to closed position,whi1e a portion of the air passes through small metering orifice 3| in the valve into the piston chamber I5 for returning the piston |1. During the impact stroke of the tool the air in front of the advancing piston forces the valve 13 downward to the position shown in Fig. 2, and passes to atmosphere through the port 13, which is unrestricted to prevent any appreciable back pressure.

The latching means for the hammer piston comprises an element 32 positioned in the pressure chamber or reservoir 21 and formed with a forwardly extending hook-like portion 33 adapted to engage the head 55 of the piston I1. The latching element 82 is pivotally mounted between the arms 53 of the supporting bracket 58 directly above the previously mentioned lever 51. Referring also to Figs. 6, 7 and 8, the supporting bracket 59 is formed with a circular flange 34, extending into the counterbore 23 in handle 24, and with a cylindrical portion 35 which extends forwardly of the flange I4 into the rear end of the cylinder Il. and provides an opening Il placing the pressure chamber 21 and the piston chamber Il in constant communication. The flange Il lies between the rear end of the cylinder I5 and the inner surface of the counterbore 23, and a locating pin 81 passes through an opening in the flange and engages associated recesses in the cylinder and handle 24 to hold these elements against relativev movement. Another opening in the flange Il connects the air passages I3 and Il.

'I'he rear end of the latching element l2 is bifurcated to form a pair of fingers 88 (Fig. 6) which engage a reduced portion 9| of a plunger 22 extending from the grip portion of the handle 24 upward into the pressure chamber 21. The fingers Il occupy 'a position between the full circular head of the plunger 92 and a collar Il which loosely surrounds the reduced portion Il of the plunger and is pressed upward by a light compression spring. M. v The plunger $2 is movable within a bushing 96 and the lower half of the plunger is hollowed out to receive a compression spring Iwhich urges the plunger upwards. 'I'he lower end of the spring $8 surrounds a supporting stem. 91 which extends below the plunger I2 into a threaded opening 9| cut in the lower end of the handle. The lower end of the stem 81 engages a recessed portion of an adjusting nut 99 movable within the opening Il. It will be evident that upward movement of the nut il will serve to increase the pressure with which the spring 8 8 urges the plunger 92 upwards, whereas downward movement of the adjusting nut servesto lessen or diminish such pressure. able length in order to minimize leakage oi' high pressure air from reservoir 21 to opening 98 which is maintained at atmospheric pressure.

As shown in Fig. 1, the plunger 82 is normally positioned with its upper convex and engaging the inside surface of the upper wall of the pressure chamber 21 while the latch 82 is maintained in engaging position by the spring pressed collar I8. The. hammer piston is, at this time, at the rear of the piston chamber and is held against forward movement by the engagement of the hook-like portion 8l, of element 82, with the head of the piston. Upon operation of the trigger I4 compressed air is admitted to the reservoir 21. Since the air has no means of escape from the pressure chamber 21 at this time the pressure in the chamber increases rapidly and, when high enough to overcome the spring 88, acts on the upper end of the plunger 92 to force it downward to the position shown in Fig. 2. In moving downward the plunger I] rocks the latching element l2 in a countercloekwise direction to disabled position. 'Ihe hammer piston is thus released and is immediately driven forward with the full force of the air trapped in the pressure chamber 21. the entire diameter of hammer piston I1 due to the loose flt of the piston within cylindrical projection li on bracket 8l. As the air in reservoir 21 expands to drive the piston it is reinforced by live air.

After the impact has been delivered and the trigger M released, the pressure chamber 21 is connected to exhaust and the plunger 82 is permitted to rise to normal position. As the hammer piston nears the end of its return stroke the head I8 thereof acts as a cam on the hooklike end of element l2, rocking the element out Bushing 95 extends for a consider-l 'I'he trapped air acts simultaneously over of its path, against' the tension of spring M. As soon as the head Il passes the portion I3. the element l2 snaps back to normal position and the piston is again latched against forward movement. Referring to Fig. 3 it will be seen that at the time the head le the hook 82. and immediately after that time, the piston is still being driven by return air since the head of the piston has not yet moved to the Fig. 4 position to make contact with the previously mentioned disabling lever I1. Upon operation of the disabling mechanism the valve 2| cuts oi! the supply of compressed air to the piston chamber I8. The piston I1 reboundsto the Fig. 1 position in which its forward movement is arrested by the hook l2; and the parts remain substantially as shown in Fig. 1 until the operator again depresses the trigger M to initiate a new cycle. 'I'he use of the latch I2 for holding the hammer piston at the rear end of the piston chamber obviates the necessity, existing in prior structures, for a continuous supply of live air to the front end of the piston chamber during the intervals between operations of the trigger. Accordingly, the present invention results in economy in the matter of air consumption.

It has previously been described how adjustment of the nut l! serves to vary the force with which the pressure responsive plunger 82 is urged to normal position. -By varying the resistance oiered by the plunger 82 to pressure within the chamber 21 the peak pressure obtainable in the chamber may be varied and the force of the blow delivered by the hammer piston thereby predetermined in accordance with the size and hardness of the rivet to be headed. In order that full advantage may be taken of this adjustable featurey a calibrated wrench is preferably used with the tool. A wrench lill for this purpose is illustrated in Figs. 9, 10 and 11 and is outlined in broken lines in Fig. 4. It comprises a cylindrical rod Ill insertable in threaded opening 98 in the grip handle 2l. 'Ihe front end of the rod has a hexagonal recess into which is pressed a projection |02 made of hexagonal wrench stock. Projection il! is adapted to fit in opening |03 in adjusting nut Il. A locating pin IM is also arranged to project from the front end of the rod IDI and is adapted `to nt a recess (not shown) in adjusting nut Il to insure alignment of the wrench with the nut always at the same angle. 'Ihe rod is turned by a handle |05 secured to its reduced end. 'I'he cylindrical part of the rod has indicia lill visible at the lower end of the grip handle. The indicia show the number of turns of the adjusting nut 99, which determines the peak pressure in reservoir A.21 and consequently the speed and momentum of the hammer piston I1. A chart prepared in terms indicative of the calibrations on the wrench and disclosing the proper setting of the nut 89 for each kind of rivet may be used to facilitate the adjustment and obtain a uniform quality of work. The chart (not shown) preferably should classify the rivets according to size, metallic composition, whether hot or cold, and whether the riveting operation is to be completed by one. two or more blows.

Having determined the proper pressure by reference to the chart, theoperator inserts the wrench ill and turns it to the left or to the right until the desired calibration appears. As long as the adjustment is unchanged, the piston will strike each rivet withv the same momentum and, ii' there is no change in the kind of rivets, with the same results. It is immaterial whether the operator pulls the lever 54 slowly or quickly. Moreover, variations in the pressure oi. the air in the factory mains will have no substantial eiect on the pressure in reservoir 21or on the accurate performance ofthe tool for the reason that the latch releasing means has the effect of a pressure limiting valve and will accurately 'supply the correct pressure in the reservoir as long as the `pressure in thehose H does not tall-'below themaximum 'required for the selected rivets.

Preferably the reservoir 21 hasU a' considerable 'volume in order that' the tool may-deliver a 'heavy blow, 1in comparison with its size, owing to the storage o! compressed air prior to the release o! hammer piston ii by the latch 82.' Upon release, the piston is' actuated not only by the live air concurrently delivered through hose H but'also by the 'expansion'of stored air in the' reservoir. As the air expands, the stored or potential energy isconverted into kinetic energy. Since the kinetic energy has only an extremely'short time in which'to build up, i. el, while-'the piston'is'moving i'orward,l it is very advantageous=that the piston may absorb potential energy at a rate exceedingthe rate of supply .ofsuch energy to the tool through the hose H and plug 28.

`While-the invention has been-herein shown and described in what is considered' to be a preierredlform,it is to'be understood that the invention is not limited to the specific details thereof but covers all changes, moclications and adaptations within the scope of the appended claims. What-is claimed is: 1.-In a pneumatic tool, the combination of a piston chamber, a piston movable therein, a pressurechamber in 'communication with said piston chamber, means for introducing pressure iiuid into said pressure chamber to'drive said piston, means for positively locking said pistonA against movement, and pressure responsive means within said pressure chamber for disabling said locking means.

2. In a device of the class described, the combination of a piston chamber, a piston movable therein, a. pressure chamber in communication with said piston chamber, means for introducing pressure fluid into said pressure chamber to drive said piston, means for latching said piston against movement, pressure responsive means within said pressure chamber for ,disabling said latching means, a yielding means opposing kmovement of said pressure responsive means, and means for adjusting said yielding means to vary the force with which movement of said pressure responsive means is opposed.

3. In a pneumatic hammer, the combination of a piston chamber. a hammer piston movable therein, a pressure chamber in communication with said piston chamber, means for introducing pressure uid into said pressure chamber to drive said hammer piston, means for locking said hammer piston against movement, and means comprising a spring pressed plunger extending lnto said pressure chamber for disabling said locking means when a predetermined degree of pressure is reachedin said pressure chamber.

4. In a device of the class described, the combination of a piston chamber, a piston movable therein,a pressure chamber in communication with vsaid piston chamber, means for introducing pressure uid into said pressure chamber to drive said piston, means movable to effective and ineffective positions for latching said piston against movement, a yielding means urging said latching means to 'effective position, and pressure responsive means vwithin said pressure chamber for moving said latching means to'ineilective position. 5.111l a device of the class describedythe combination of a piston chamber, a piston movable therein, a pressure chamber in communication withsaid pistonrchamber, means'for introducing pressure iiuid into -said pressurechamber to drive said piston, means movable to effective and ineilective positions for latching said piston against movement, a yielding means urging said latchingmeans to effective position, pressure responsive means within said pressure chamber forV moving said latching means to inefi'ectiveposition, and a yielding means-of variable strength resisting operation of said pressure responsive means.' l

6; In a device o! the class described, the combination of a cylinder, a piston chamber withinsaid cylinden-a handle connected to one end of said cylinder, a pressure chamber within said handle and in communication with said piston chamber, a piston'movable within said piston chamberand projecting into said pressure chamber when positioned at one end of said piston chamber, means for introducing pressure fluid into. said pressure chamber to move said piston from one end to the other of said piston chamber, means for mechanically locking said piston .against movement, and pressureresponsive means Iwithin-said pressure chamber for disabling said locking means.

7. In a device oi the class described, the combination of a cylinder, a piston chamber within said cylinder, a .handle connected. to one end of said lcylindbr, a pressure chamber within s aid handle andin communication with said piston chamber, a piston movable within said piston chamber and projecting into said pressure chamber when positioned at one end of said piston chamber, means for introducing pressure iiuld into Ysaid pressure chamber to move said piston from one end to the other o f said piston chamber, and pressure responsive means within said pressure chamber for preventing movement oi said piston until a predetermined degree of pressure is reached in said pressure chamber, said means including a latch adapted to engage said piston and a spring pressed plunger movable under the force of pressure uid in; a direction to disable said latch.

8. In a device of the class described, the combination of a piston chamber, a piston movable therein, means for introducing pressure fluid into said piston chamber toeiect a reciprocating motion of said piston, means for controlling the flow o! pressure fluid to said pis'ton chamber including a throttle valve settable from a normal position to a plurality of operating positions, means for latching said throttle valve in one of its operating positions, and means operable by said piston for disabling said latching means.

9. In a device oi' the class described, the combination of a'piston chamber. apiston movable within said chamber, means for introducing pressure uid into said piston chamber to effect a reciprocating motion oi' said piston, means for controlling the iiow oi pressure iluid to said piston chamber including a throttle valve settable from a normal position to a plurality ot actuated positions in one of which actuated positions pressure iiuid is admitted to said piston chamber in a direction to move said piston through a driving stroke and in another o! which actuated positions pressure iluid is admitted to said piston chamber in a direction to move said piston through a return stroke, means for latching said' throttle valve in its said last mentioned position, and means operable by said piston at the end of its return stroke for disabling said latching means.

10. In a throttle mechanism for a pneumatic tool, the combination oi' a bore, means for conducting pressure fluid to said bore, a valve bushdng within said bore, a piston valve movable within said bushing, a valve opening within said piston valve, a port establishing communicationv opening and movable relatively to said valve from an ineii'ective to an eii'ective position to close said second port. a yielding means urging said plunger to ineffective position, a manually operable lever adapted during a part of its stroke to depress said plunger to eiiective position and during another part of its stroke to depress said valve and said plunger as a unit to admit air to said valve opening. and means independent of said manually operable lever for latching said valve in depressed position.

11. A pneumatic percussive tool comprising a cylinder providing a piston chamber, a hammer piston reciprocable therein, an inlet for live air, a manrelly operated throttle valve arranged upon operation thereof to distribuite live. air from said inlet to the rear part of the piston chamber to drive the piston forward, automatic means responsive to the release o! the throttle valve for deliveringr live air to the front part of the piston chamber to return the piston. and means automatically discontinuing such delivery of air to the front part of the piston chamber upon completion oi' the return stroke oi' the piston.

12. A pneumatic percussive tool comprising a cvlinder providing a piston chamber, a hammer piston reciprocable therein, an inlet for live air, a manually operated throttle valve arranged upon operation thereoi' to distribute live air from said inlet to the. rear nerf. nf the. piston chamber to drive the piston forward, automatic means responsive to the release of the throttle valve fnr delivering live air to the front part of the piston chamber to return the piston. means automatically discontinuing such delivery of air to the front part oi' the piston chamber upon comnletion oi the return stroke of the piston, and means for positively locking the piston near the rear `end of the piston chamber just prior to the completion of the return stroke.

13. A iluid pressure percussive tool of the single impact type comprising a piston chamber having a reciprocable piston therein. amanually operated throttle valve adapted when in operated position to deliver live pressure iiuid to the rear end of the piston to tend to drive it forwardly, means restraining the piston against forward movement while the throttle valve is being operated and while the resultant o! uid pressures in all directions on the piston is in a forward direction and of substantial magnitude. and iluid pressure responsive means for disabling said restraining means.

14. A iiuid pressure percussive tool according to claim 13 in which the restraining means comprises a mechanical latch and in which said disabling means operates when the pressure on the rear end oi the piston attains a predetermined va ue.

15. A percussive air operated riveting tool of the one-shot or single impact type comprising a cylinder having a hammer piston reciprocable therein, an energy accumulator associated with said cylinder. means for positively holding said hammer piston against movement while energy is supplied to said accumulator prior to the start oi' the impact stroke of the piston, and means for delivering such accumulated energy to the piston and simultaneously supplying live air to' the rear of the piston during the impact stroke thereof.

16. A percussive air operated riveting tool of the one-shot or single impact type comprising a cylinder having a hammer piston reciprocable therein, an air reservoir having a volume exceeding that of the piston and communicating with the rear end of the cylinder, means for eimultaneously holding the piston at the rear end oi' the cylinder and delivering live air to the reservoir, means i'or releasing the piston ai'ter pressure has been built up in the reservoir, and means for driving the piston forward. subsequent to such release. by the concurrent action oi live air and stored air i'rom the reservoir.

17. A percussive air operated tool of the single action type comprising a cylinder, a hammer piston reciprocable therein, an air reservoir having a volume considerably in excess oi'-the volume of the piston and communicating with said cylinder. means i'or delivering live air to the reservoir, means for restraining said piston against movement while air is stored in said reservoir, and control means for disabling said restraining means to cause said piston to be driven by stored air expanding from the reservoir into the cylinder.

18. A percussive air operated tool of the single I action type comprising a cylinder, a piston reciprocable therein through a power stroke and a return stroke, means for directing compressed air to the rear i'ace ol.' the piston to drive said piston on its power stroke, means for restraining said piston against movement on its power stroke, and pressure responsive means i'or disabling said restraining means when the pressure acting on said piston rises to a predetermined height.

19. A percussive air operated tool according to claim 18, including adjusting mechanism for increasing and reducing the resistance of said pressure responsive means to actuation.

20. In a pneumatic tool. the combination o! a piston chamber, a piston reciprocable within said piston chamber through a power stroke and a return stroke, a pressure chamber in communication with said piston chamber, means for introducing pressure uid into said pressure chamber to drive said piston on its power stroke.

' means-for restraining said piston against movement on its power stroke, and means operable upon attainment of a predetermined pressure in said pressure chamber for disabling said restraining means.

21. A percussive tool of the single action type. comprising a cylinder, a hammer piston reciprocable within said cylinder and normally held at one end thereof, an energy accumulator acting to deliver energy to said piston, means for supplying energy to said accumulator while said 22. A percussive tool of the single action type according to claim 21, including means for controlling operatlon of said releasing means to vary at will the amount of energy which may be stored in said accumulator prior to the release 10 of said piston.

OMAR E. CLARK.

v CERTIFICATE oF CORRECTION. patent No. 2,2h1,18l;. May 6, 19M

' oma E. CLRK.

It is hereby certified that error appears in the printed specification ofthe above numbered patent requiring correction as follows: Page 1+, first column, 11n@ h2, for "and" read -end; page 6, -Ijirst column, line 2li, claim lO, for the word "part" read -port; line 52, cl'aim ll, after "piston" second occurrence; strike out the'period and insert instead a comma; and that the said Letters Patent should be read with this correction therein that the same may'conform to the record of the case in the Patent office.

signed'and sealed this 5rd day of June, A. D. 19in.

Henry Van Arsdale, (Seal) Acting Commissioner of Patentm 

